Commercially available herbicide compositions include a very large variety of active herbicide compounds. Herbicide compositions can be prepared from a variety of different types of precursor compositions, and can be commercially available and used in a variety of different types of compositions, including compositions referred to as wettable powders, water dispersible granules, granules, aqueous solutions, water soluble powders, emulsifiable concentrates, oil-based flowables, concentrated emulsions, suspo-emulsions, emulsions, suspensions, suspension concentrates, mixtures, dispersions, and microemulsions, as well as others. Any of these different types of compositions may have different advantages or disadvantages depending on what type of active ingredients the herbicide includes.
Many of these compositions contain water-soluble salts of chlorinated carboxylic acid herbicides. These salts, often alkylamine salts or metal salts, are generally not as active as their acid equivalents. For example, (2,4-dichlorophenoxy)acetic acid (“2,4-D”) acid is known to be more herbicidally active than the dimethylamine salt of 2,4-D. Also, many of the chlorinated carboxylic acid herbicides are sold to the end users as esters because these esters are more active than the corresponding amine formulation. For instance, it is generally known that 2,4-D ester formulations are more effective as herbicides than 2,4-D amine formulations. The esters, however, are more likely to volatilize even after deposition onto target areas. After volatilization, these esters can cause significant damage to off-target plants.
Acid herbicides are usually have traditionally been reacted into amine or other salts, which are soluble in water, or into esters which are oil soluble. Both salts and esters must then break down in the environment back into the acid, which is herbicidal.
It would be preferable, then, to apply the herbicides as acids. However, they are not significantly soluble in water. Previously, solvents used to formulate 2,4-D acid such as xylene range hydrocarbons, are known to be phytotoxic to plants and may enhance herbicide volatility and subsequent drift to non-target areas. Albaugh D-638 is one such product, but it further incorporates the ester form of 2,4-D into the formulation. The formulation is 24.5% by weight of 2-butoxethyl ester of 2,4-dichlorophenoxyacetic acid (CAS #1929-73-3), 13.8% by weight 2,4-D (CAS #94-75-7) and a solvent that contains 7.7% by weight naphthalene (CAS #91-20-3). It is believed that the solvent is Aromatic 150. It is believed that solvent is present in an amount from 55 to 60%. Another commercial product containing the acid form of 2,4-dichlorophenoxyacetic acid is WEEDONE® 638 from Rhone Poulenc (now marketed by Nufarm). This formulation contains 25.2% of the 2-ethylhexyl ester of 2,4-D, 13.8% of the acid form of 2,4-D, 3% propylene glycol, 1.5% titanium oxide and other undisclosed inerts. This formulation is believed to be described in one of the following patents: U.S. Pat. Nos. 5,254,344, 5,096,711, or 5,206,021. The 2,4-D in this formulation is not solubolized, but has been dispersed through a water phase.
Another problem associated with the amine salts of some chlorinated carboxylic acid herbicides is their inability to mix with fertilizers. 2,4-D amine herbicides cannot be mixed directly into Uran (urea-ammonia nitrate) fertilizer without some dilution in water. This is a disadvantage for applicators, since this dilution practice increase the total spray volume they must apply per acre.
Surfactants are used in most agricultural formulations to enhance the ease of application. Since many pesticide formulations use hydrophobic solvents, requiring the use of surfactants to emulsify the hydrophobic solvent and pesticide into water. Surfactants have also been used both as adjuvants and formulation components to enhance the effectiveness and spreading ability of applied sprays.
Examples of just a few available active herbicide compounds include those herbicides from the class of the hydroxylamines, for example sethoxidim, alloxydim, clethodim, cycloxydim, tepralkoxydim, tralkoxydim or butroxidim;
herbicides from the class of the imidazolinones, such as imazethapyr, imazamethabenz, imazamethapyr, imazaquin, imazamox or imazapyr;
herbicides from the class of the pyrimidines, such as pyrithiobac-sodium, pyriminobac, bispyribac-sodium;
herbicides from the class of the PPO, for example nitrofen, bifenox, acifluorfen, lactofen, oxyfluorfen, ethoxyfen, fluoroglycofen, fomesafen, halosafen, azafenidin (CAS RN.-68049-83-2), benzfendizone (CAS RN 158755-954), butafenacil (known from U.S. Pat. No. 5,183,492, CAS RN 158755-95-4), carfentrazone-ethyl, cinidon-ethyl (CAS RN 142891-20-1), flumichlorac-pentyl, flumioxazin, fluthiacet-methyl, oxadiargyl, oxadiazon, pentoxazone, sulfentrazone, fluazolate (CAS RN 174514-07-9) or pyraflufen-ethyl;
herbicides from the class of the phenoxy acids, for example 2,4-D, Monochloro phenyoxy acidic acid (MCPA), Monochloro phenyoxy propionic acid (MCPP), MCPB, trichlorpyr or mecropop-P;
herbicides from the class of the benzoic acids, for example dicamba or picloram; herbicides from the class of the sulfonamides, for example flucarbazone (CAS RN 181274-17-9), procarbazone (CAS RN 145026-81-9), chlorasulam, diclosulam (CAS RN 145701-21-9), florasulam, flumetsulam or metosulam;
Herbicides from the class known as pyridine herbicides, (e.g., triclopyr, fluoroxypyr);
Herbicides from the class of benzoic acid herbicides, (e.g., dicamba acid);
herbicides from the class of aryloxy phenoxy propionic acid herbicides, (e.g., fluazifop acid and quizolofop acid); and
water-insoluble diphenyl ether type herbicides (e.g., oxyfluorfen or acifluorfen).
Active herbicide ingredients such as these and others can be prepared from and used in the form of solid and liquid compositions including, as mentioned above, different forms of emulsions, suspensions, suspension concentrates, mixtures, dispersions, and microemulsions, etc. With regard to the liquid forms, the active ingredient (herbicide compound) is generally suspended or dissolved in a liquid, with the active herbicide compound taking the chemical form of a salt or ester, depending on which form is either soluble or suspendable in such a liquid composition. Most herbicide compositions are prepared from an ester or salt form of a herbicide compound, or are prepared using a step to convert an acid form of a herbicide compound to a salt or an ester to be either miscible in water or emulsifiable in water for application, often with the assistance of organic solvent.
With microemulsion compositions, in particular, earlier microemulsion work typically included the use of herbicide compounds in forms other than their acid forms, e.g., ester or salt forms, because the salt or ester forms were considered to be most easily dispersed or suspended in a microemulsion. Typical microemulsions also incorporated organic solvents to effect suspension or dissolution of the herbicide compound.
New forms of effective herbicide compositions are always desirable, especially those that show advantages in processing, application, environmental profile (e.g., volatility), or efficacy. And there is always a desire to prepare herbicide compositions that reduce or eliminate organic solvents.
U.S. patent application Ser. No. 09/916,611 describes an invention wherein the chlorinated carboxylic acid herbicide is dissolved in a surfactant. The examples provided in this application demonstrate the use of alcohol ethoxylates in most of the examples. In examples 2 through 5, other surfactants are used in place of the alcohol ethoxylates. The specific alcohol ethoxylates used were C11 alcohol with 3 moles of EO and C11 alcohol with 9 moles of EO. These alternate surfactants are nonylphenol 6 mole ethoxylate, a block copolymer (Pluronic), a sorbitan based surfactant, butyl cellusolve, and a phosphate ester of a C11 alcohol with 6 moles of EO.
U.S. Pat. No. 6,803,345 (Herold, Beardmore and Parrish), describes herbicide compositions that are prepared from micro-emulsions containing herbicide compound in acid form, and methods of their preparation and use. There are other patents and applications in the U.S. and internationally that are related to this patent. These formulations also contain acid herbicides which are dissolved in surfactants. There are a number of examples shown in this patent. Nearly all of the examples provided include as major constituents, alcohol ethoxylates. Specifically, Tomadol 1-5, Tomadol 1-7, Surfonic L12-6 are used as major constituents of the first 17 examples. The next set of 5 examples use alternate surfactants. Specifically, in place of the alcohol ethoxylates of the first 17 examples, the surfactants are octyl- or nonyl-phenol ethoxylates, a castor oil ethoxylate, sorbitan based surfactants, or ethoxylated tristerylphenol.
In both patents, in all examples where alcohol ethoxylates were used, the specific alcohol ethoxylates contain high levels of free alcohol.
Surfactant used inexamples shown inprior application andpatent% Free alcoholReferenceC11-3 EO16%Tomah Products, Inc. Brochure entitled:Tomadol Alcohol Ethoxylate ProductGuide, no date given.C11-9 EO 2%Tomah Products, Inc. Brochure entitled:Tomadol Alcohol Ethoxylate ProductGuide, no date givenTomadol 1-5 5%Tomah Products, Inc. Brochure entitled:(C11-5EO)Tomadol Alcohol Ethoxylate ProductGuide, no date givenTomadol 1-7 3%Tomah Products, Inc. Brochure entitled:(C11-EO)Tomadol Alcohol Ethoxylate ProductGuide, no date givenSurfonic L12-6Estimated at 5-7%No data available from Hunstman. Data(C10-12 -6EO)extrapolated from Tomah similar productin above reference.Surfonic DDA-6Estimated at 5-7%No data available from Hunstman. Data(Dodecyl alcoholextrapolated from Tomah similar product(branched)-6EO)in above reference.Surfonic TDA-6Estimated at 5-7%No data available from Hunstman. Data(Tridecyl alcoholextrapolated from Tomah similar product in(branched)-6EO)above reference.
From the number of examples shown in the previous literature, it is clear that the C11 alcohol ethoxylate was the most favorable surfactant.
It has been surprisingly discovered that the free alcohol in alcohol ethoxylates is capable of reacting with the acid herbicides of the prior inventions. Also, the free alcohol commonly mixed with some surfactants, such as phosphate ester surfactants, can react with acid herbicides.
Previously, it was expected that the compositions would require temperature extremes as high as 200 degrees F. in order to make the alcohol and acid herbicide react. It has been found that this reaction occurs, albeit more slowly, at elevated temperatures much lower than 200 degrees F., and even at ambient temperatures. The reaction product of this free alcohol and acid herbicide is generally an ester of the acid herbicide. Ester forms of acid herbicides are generally much more volatile than their acid or amine forms.
It is possible to formulate acid herbicide compositions with little or no free alcohol. In this manner, the alcohol-acid herbicide reaction and decomposition is prevented.
One way of identifying a herbicide compound in acid form is to reference a pKa of a herbicide compound. The pKa of a herbicide compound is understood to refer to the negative logarithm (base 10) of the equilibrium constant K for the reaction of the herbicide compound between its acid form and its neutral form. Methods of determining the pKa for a herbicide compound will be readily understood by the skilled artisan. Exemplary herbicide compounds that are capable of existing in acid form can have a pKa below about 6, or below about 5 or 4. Some herbicide compounds include more than one acidic hydrogen and therefore have more than a single pKa value. According to the invention, the relevant and referred to pKa is the pKa of a herbicide compound that relates to the change of the compound between the compound considered to be the deprotonated “acid” form of the compound, and what is considered to be the protonated (neutral) form of the “acid” form. The protonated acid form predominates at pH below the pKa, and the deprotonated form predominates at pH above the pKa. Examples of exemplary pKa values for certain herbicide compounds are included in the Table 1.
Some examples of useful herbicide compounds that can be used in their acid forms to produce microemulsion-forming-concentrates (MFC) in surfactant include the following, some or all of which are commercially available in their acid form (though presently not generally sold in that form as herbicide formulations). For herbicide compounds that are sold in a form other than the acid form, such as a salt or ester form, a skilled chemist will understand how to convert the non-acid to an acid form for use as described herein. For example, depending, e.g., on the herbicide compound and other factors, from about 0.05 to about 7 parts by volume MFC may be diluted with about 93 to about 99.95 parts by volume water to form a microemulsion. Other ingredients such as acidifying agent or other herbicides may also be added.
The class of phenoxy herbicides generally includes herbicides derived from chlorinated phenols, and includes herbicide compounds that can exist in an acid form. Examples include the well known herbicides 2,4-dichlorophenoxyacetic acid (known as 2,4-D), 4-methyl-4-chlorophenoxyacetic acid (MCPA Acid), and 2(-2-methyl-4-chlorophenoxy)propionic acid (MCPP acid), as well as others.
Pyridine herbicides are herbicides derived from a pyridine ring-containing compound, and includes herbicide compounds that can exist in an acid form. Examples include 3,5,6-trichloro-2-pyridyloxyacetic acid (triclopyr acid) and fluroxypyr (4-amino-3,5-dichloro-6-fluoro-2-pyridyloxyacetic acid), as well as others.
Benzoic acid herbicide compounds include or are derived from benzoic acid compounds. This class of herbicide compounds includes herbicide compounds that can exist in an acid form. A single example is dicamba acid (3,6-dichloro-O-anisic acid), but others could also be used according to the invention.
Aryloxy phenoxy propionic acid herbicide compounds (also referred to sometimes as “oxyphenoxy” herbicides), are another class of herbicides that can exist in an acid form. Examples of specific compounds include fluazifop acid and quizolofop acid, as well as others.
TABLE 1Acidic Herbicides:pKasBromoxynil4.06Ioxynil3.96Bentazon3.30Dicamba1.87Diclofop3.57FenoxapropNAFluazifop-p2.98FosamineNAGlufosinate2, 2.9Glyphosate2.6, 5.6Haloxyfop2.9Imazamethbenz2.9Imazapyr1.9, 3.6Imazaquin3.8ImazamoxNAImazethapyr2.1, 3.9Picloram2.3Triclopyr2.68, 3.97Clopyralid2.3Floroxypyr2.94Quinclorac4.34Quizalofop-p1.25Sethoxydim4.162,4-D2.642,4-DB4.8Dichlorprop3.0MCPA3.07Mecoprop3.77ClethodimAcifluorfen3.86DacthalNAEndothal3.4, 6.7Asulam4.82(Where a pKa is listed as NA, a person of ordinary skill in the art would be able to identify the pKa.)
The herbicide compound in acid form is dissolved in surfactant (and optionally water and organic acid) to form a concentrate that contains surfactant and dissolved herbicide compound in acid form.
Provided that they do not contain free alcohol, additional surfactants can be added to this composition. A very large variety of surfactants are known and commercially available, including such different classes as cationic surfactants, anionic surfactants, non-ionic surfactants, ionic surfactants, and amphoteric surfactants. According to the invention, the surfactant can be any surfactant or combination of two or more surfactants useful to dissolve the herbicide compound in its acid form to produce a microemulsion-forming-concentrate.
Examples of some preferred additional surfactants that can be added to this composition include cationic, non-ionic, and anionic surfactants. Of these, some even more specific types of preferred surfactants include non-ionic linear or branched alcohol ethoxylate surfactants, anionic phosphoric acid ester surfactants (sometimes referred to as “phosphate ester” surfactants), and cationic ethoxylated tallow amine surfactants. Examples of surfactants and identification of their intermediate and general classifications are as follows:
Alcohol alkoxylates including but not limited to:
Based on branched and linear alcohols
Those containing ethylene oxide or propylene oxide
Alcohol alkoxylate sulfates,
Alkylphenol alkoxylates including but not limited to:
Nonylphenol and octylphenols.
Those containing ethylene oxide or propylene oxide
Alkanolamides,
Alkylaryl sulfonates,
Amine oxides
Amines including but not limited to:
Fatty amine alkoxylates such as but not limited to tallowamine alkoxylates,
Betaine derivatives,
Block polymers of ethylene and propylene glycol,
Carboxylated alcohol or alkylphenol alkoxylates,
Diols, including but not limited to Butanediols,
Diphenyl sulfonate derivatives,
Ethers, including but not limited to
Butyl celluslose,
Butyl carbitol,
Ethoxylated amines,
Ethoxylated fatty acids,
Ethoxylated fatty esters and oils,
Ethoxylated triglycerides,
Fatty esters,
Glycerol esters,
Phosphate ester surfactants including but not limited to
Phosphate esters of alcohol alkoxylates,
Phosphate esters of alkylphenol alkoxylates,
Sarcosine derivatives,
Silicone-based surfactants,
Sorbitan derivatives including but not limited to:
Sorbitan esters,
Alkoxylated sorbitan esters,
Sucrose and glucose derivatives including but not limited to:
Alkylpolyglucosides,
Sulfates and sulfonates of alkoxylated alkylphenols,
Sulfates of alcohols,
Tristyrylphenol Alkoxylates,
Other surfactants are disclosed in McCutcheon's Emulsifiers and Detergents, North American Edition, 2000.
The following examples were prepared: